It is known that the filtration of very fine (superfine) dusts which have a particle size smaller than 5 .mu.m, especially carbon particles emitted by diesel engines which have a particle size smaller than 0.5 .mu.m and fine particles in slurries, presents special technical problems. For example, an attempt is being made at present to filter the carbon black from diesel engines with porous, ceramic honeycomb bodies of a type similar to catalyst carriers in which every second conduit is closed on one side of the front surface. In this type of filter, the carbon particles are burned periodically with the aid of a supplementary heating when the pressure loss of the filter is several hundred millibars. This device has a high heat capacity.
U.S. Pat. No. 2,061,370 teaches that small amounts of rare earths in ferritic heating conductor alloys exert a favorable influence on the oxidation resistance, especially on the adhesion strength, of oxide layers. The same applies to the elements yttrium, titanium and zirconium as alloy additives. Aluminum oxide fringe crystals (whiskers) are grown from such alloys with the aid of a two-stage oxidation (see British Patent 2,081,747). The manufacture of catalytic honeycomb bodies is mentioned as a potential application for these aluminum oxide whisker foils and the whiskers have the function of enlarging the adhesive surface and of raising the adhesive strength of further coats of ceramic powders (wash coat). Nothing can be learned from this publication concerning the use of such alloys for filter purposes.